Nitrogen dynamics in the soil-plant system under deficit and partial root-zone drying irrigation strategies in potatoes

Abstract: Experiments were conducted in lysimeters with sandy soil under an automatic rain-out shelter to study the effects of subsurface drip irrigation treatments, full irrigation (FI), deficit irrigation (DI) and partial root-zone drying (PRD), on nitrogen (N) dynamics in the soil-plant system of potatoes. In 2005, FI and PRD2 were investigated, where FI plants received 100% of evaporative demands, while PRD2 plants received 70% water of FI at each irrigation event after tuber initiation. In 2006, besides FI and PRD2 treatments, DI and PRD1 receiving 70% water of FI during the whole season were also studied. Crop N uptake and residual NH 4-N and NO3-N to a depth of 0–50cm, at 10cm intervals were analyzed. For both years, the PRD2 treatment resulted in 30% water saving and maintained yield as compared with the FI treatment, while when investigated in 2006 only, DI and PRD1 treatments resulted in significant (P <0.05) yield reductions. In 2005, the soil residual N content at harvest was significantly 29% lower with PRD2 than for FI in the whole root zone; and leaf N concentration for PRD2 was significantly higher than for FI. In 2006, soil residual N content at harvest was 33% lower with PRD2 than for FI, which was not significant however. In the late season, reflectance vegetation index and leaf area index for the water saving treatments were higher than for the FI treatment. For both years the PRD2 treatment had the lowest residual N content in the root zone. We conclude that: (1) of the investigated water saving irrigation strategies (PRD1 PRD2, DI) PRD imposed just after tuber initiation until maturity (PRD2) was the only strategy able to maintain yield; thus, soil drying induced by PRD or DI treatments should be avoided during early growth stages; (2) the PRD and DI treatments improved soil nitrogen availability late in the growing season maintaining top ‘greenness’ to a greater extent, as compared with FI. [Copyright &y& Elsevier]